Influences of the magnetic coupling process on the spectrum of a disk covered by the corona

Department of Physics, Huazhong University of Science and Technology, Wuhan 430074, PR China e-mail: dxwang@hust.edu.cn

Received: 23 September 2005
Accepted: 23 January 2006

Abstract

Context.Recently, much attention has been paid to the magnetic coupling (MC) process, which is supported by the very high emissivity indexes observed in Seyfert 1 galaxy MCG-6-30-15 and GBHC XTE J1650-500. But the rotational energy transferred from a black hole is simply assumed to be radiated away from the surrounding accretion disk in the black-body spectrum, which is obviously not consistent with the observed hard power-law X-ray spectra.

Aims.We introduce a corona into the MC model to make it more compatible with observations.

Methods.We describe the model and the procedure of a simplified Monte Carlo simulation, compare the output spectra in the cases with and without the MC effects, and discuss the influences of the three parameters involved in the MC process on the output spectra.

Results.It is shown that the MC process augments radiation fluxes in the UV or X-ray band. The emergent spectrum is affected by the BH spin and magnetic field strength at the BH horizon, while it is almost unaffected by the radial profile of the magnetic field at the disk.

Conclusions.Introducing corona into the MC model will improve the fitting of the output spectra from AGNs and GBHCs.